The increasing need for sustainable energy storage has rekindled interest for Na-ion batteries. Their energy density can be enhanced using anionic redox (AR), as reported in Na-deficient P2 phases. Contrary to their Li-rich counterparts with O3 stacking, these Na-deficient P2 phases show surprisingly good structural stability during AR. Understanding the fundamental relationship between O and P stacking and AR reversibility thus becomes critical. Herein, using density functional theory (DFT) analysis and modeling of O2- and P2-Na_2∕3Mg_1∕3Mn_2∕3O₂, we show that during AR, the oxygen network is stabilized through either (1) a highly reversible collective distortion, in P stacking, or (2) a disproportionation of oxygen pairs leading to voltage hysteresis, in O stacking. Using this 2-distortions model, we describe a magnetic-constrained DFT methodology to predict the critical state of charge for reversible cycling that we successfully extend to other Mn-based cathodes. This article provides fundamental understanding, powerful computational methods, and practical guidelines to design next-generation cathode materials.

可持续能源存储的需求不断增长，重新引起了人们对钠离子电池的兴趣。如缺钠的P2相中所报道的，可以使用阴离子氧化还原（AR）来提高其能量密度。与富锂的O3堆积相反，这些Na缺乏的P2相在AR中表现出令人惊讶的良好结构稳定性。因此，了解O和P堆叠与AR可逆性之间的基本关系变得至关重要。在此，使用密度泛函理论（DFT）对O2-和P2-Na _2∕3 Mg _1∕3 Mn _2∕3 O ₂进行建模和建模，我们表明，在AR期间，氧网络通过（1）在P堆中高度可逆的集体畸变或（2）在O堆中导致电压滞后的氧对歧化来稳定。使用这种2变形模型，我们描述了一种磁约束DFT方法，以预测可逆循环的临界电荷状态，并将其成功扩展到其他基于Mn的阴极。本文提供了设计下一代阴极材料的基础知识，强大的计算方法和实用指南。